The present invention relates generally to bubble memory systems of the field access type which are now well known. More particularly, this invention relates to the coupling of the propagation track or shift register to a plurality of bubble idlers formed as an array to form a noncirculating, or stationary register which may be controllably accessed by means of a single current loop.
Generally, the storage within a bubble memory system is of the circulating type whereby in response to an in-plane rotating magnetic field bubble elements traverse a path in a magnetic material controlled by an overlayer of magnetic elements. Thus, the memory is circulating in nature, typically in a major loop, minor loop configuration whereby the contents of a plurality of minor loops may be accessed controllably by a single major loop. However, it appears desirable to have also available in connection with such systems a certain capacity of memory which is noncirculating and may in effect be stored like a holding register. However, it is necessary to have the contents of this storage register available for use together with a facility for altering the contents of the register.
Various propagation tracks comprising elements of different shapes are well known in the bubble memory art. Perhaps the best known and oldest is the so-called T-bar type. Similarly, various arrangements of bubble idlers are known in the art, typically consisting of an arrangement of line bars all pointing to a central location. For example, U.S. Pat. No. 3,803,564 shows both the T-bar propagation track system, together with the sequential steps followed by a bubble in traversing such a track in the presence of a rotating magnetic field. Further, that patent also shows a typical bubble idler arrangement. However, that patent does not show a means for coupling a propagation track to the idler arrangement like that of the present application. The idler arrays in that patent are formed to operate in a passive function where the array functions as a data compressor and bubble-bubble interaction is used to perform logic operations.
As a point of reference, U.S. Pat. No. 4,020,476 shows a particularly specialized conductor loop arrangement for controlling the transfer of a bubble from one location, in a minor loop, to another location in a major loop. Conductor loops of various sorts are typically used for transferring bubble from major to minor loops and vice versa. However, applicant is not aware of the use in the prior art of a conductor loop in connection with controlling the contents of a bubble idler array.